Adhesive compositions are used to affix (bond) glass (windows) into buildings and vehicles, see Rizk, U.S. Pat. No. 4,780,520; Bhat, U.S. Pat. No. 5,976,305; Hsieh et al., U.S. Pat. No. 6,015,475 and Zhou, U.S. Pat. No. 6,709,539, all incorporated herein by reference. In automobile factories windows are installed using robots and computer controlled processing. This facilitates the use of a variety of high performance adhesives used on a variety of automobiles, for instance nonconductive adhesives and high modulus adhesives. It is also difficult to formulate a high performance adhesive that does not sag, that is, lose the shape of the adhesive bead applied to the vehicle or the glass. Thus many commercial processes utilizing adhesives to bond windows into vehicles require the use of some means of fixturing the glass in place until the adhesive has enough strength to hold the window in place. The means of fixturing windows in place until the adhesive cures results in added cost. Thus it is desirable that the adhesive used to bond the glass in place be capable of holding the glass in place upon application of the adhesive.
Adhesives have been developed which provide good initial green strength that allows the adhesive to hold the glass in place without additional fixturing to hold the glass in place. This is achieved through the inclusion of crystalline thermoplastic polymers, such as polyesters, in the adhesive. These adhesives have hot melt properties that require that the adhesives to be melted and applied hot. As the adhesive cools the thermoplastic portion crystallizes and provides initial green strength to hold the glass in place, see Proebster, U.S. Pat. No. 5,747,581, incorporated herein by reference. The problem with these adhesives is that they cure too slow and do not provide enough green strength to prevent movement of glass. Also formulations disclosed in the reference require a relatively high amount of the thermoplastic component. High amounts of the thermoplastic material can negatively impact the physical properties of the cured adhesive.
What is needed is a composition which is useful as an adhesive for bonding glass into a structure which exhibits fast strength development and good long term properties and does not sag when applied.